This invention relates to a light-sensitive direct posi silver halide photographic material, more particularly to a light-sensitive color photographic material having an internal latent image type silver halide emulsion layer capable of giving a direct posi image by subjecting the whole surface to exposure or carrying out surface development in the presence of a fogging agent, after image exposure.
Methods for obtaining direct posi images known in the prior art can be classified mainly into two types. In one of them, a silver halide emulsion having previously fogged nucleus is employed and posi image is obtained after development by destroying the fogged nucleus or the latent image at the exposed portion by utilizing solarization or Hershel effect, etc. In the other type, an internal latent image type silver halide emulsion not previously subjected to fogging is employed, and fogging treatment (treatment for forming developing nucleus) is applied after image exposure and then surface development is performed, or alternatively surface treatment is performed while applying fogging treatment (treatment for forming developing nucleus) after image exposure, whereby a posi image can be obtained.
The above fogging treatment (treatment for forming developing nucleus) may be conducted by way of giving the whole surface exposure, chemically by use of a fogging agent, or by use of a strong developing solution, or further by heat treatment, etc.
Of the above two methods for formation of posi images, the methods of the latter type are generally higher in sensitivity than the methods of the former type and therefore suitable for uses in which high sensitivity is required.
In this field of the art, various techniques have been hitherto known. For example, there have been known the methods disclosed in U.S. Pat. Nos. 2,592,250, 2,497,875, 2,588,982, 3,761,266, 3,761,276, 3,796,577 and U.K. Pat. No. 1,151,363.
Although a light-sensitive photographic material for forming a posi image can be prepared by use of these known techniques, it has been desired to further improve photographic performance and solve the problems in manufacture in order for these light-sensitive photographic materials to be applied for various kinds of photographic fields.
In this field of the art, it has been widely known to produce a light-sensitive direct posi photographic material by use of two or more kinds of internal latent image type emulsions. For example, U.S. Pat. No. 4,035,185 discloses mixing of the core/shell type emulsions in which the extent of internal chemical sensitization is varied, but the emulsion which has been internally chemically sensitized to deeper extent is not sufficient in the effect of posi image formation. Thus, even a mixed emulsion is desired to attain still higher maximum density.
Japanese Unexamined Patent Publications Nos. 111938/1983 and 77436/1984 disclose mixing and overlaying of the core/shell type emulsion and the fine particulate emulsion. However, the fine particulate emulsion alone cannot form an image, but it is merely provided for improvement of coating power. Therefore, photographic performances possessed by the respective emulsions cannot be fully utilized, and the minimum density is also high.
Also, in the silver halide emulsion layer having substantially the same light-sensitive wavelength region, by mixing internal latent type silver halide emulsions with different grains or coating of such emulsions in separate layers, a broad exposure latitude can be obtained or gradation can be controlled. However, since grains with different grain sizes are different in progress of development, gradation of so called poor continuation differing greatly between gradation at the leg portion and gradation at the shoulder portion may be obtained, and the results may not be necessarily satisfactory with respect to stability when the development processing conditions are varied.
It has also been desired in the prior art to improve image quality of the light-sensitive silver halide color photographic material (hereinafter called color photographic material), above all sharpness. Particularly, in the case of a direct posi color photographic material, it has been found that sharpness is further deteriorated. Although the cause has not yet been clarified, it may be speculated as follows. That is, after image exposure of the direct posi color photographic material, developed nucleus is formed on the silver halide surface by subjecting the whole surface to exposure or carrying out surface development in the presence of a fogging agent. Accordingly, after the developed nucleus is formed, an abrupt developing reaction occurs, causing the oxidized product of the color developing agent to accumulated at high concentration and deteriorate image quality of the color developed dye image. Also, image quality deterioration, which becomes more marked as the development processing time is shortened, is an obstacle against rapid processing.
Such image quality deterioration cannot be reduced to give fully satisfactory good image quality by optical means such as inclusion of a water-soluble dye in a color photographic material.
Accordingly, the object of the present invention is to provide a direct posi color photographic material with improved processing stability, having smooth gradation and excellent image quality, in which the respective photographic performances of the internal latent type silver halide grains with different grains sizes are fully utilized.